Multiband resonant system wherein each band is step-wise tunable



Aprll 1952 c. L. RICHARDS ETAL 2,591,965

MULTIBAND RESONANT SYSTEM WHEREIN EACH BAND IS STEP-WISE TUNABLE Filed Aug. 5, 1947 CHANGEOVER swrrcw 21 "(5' O I ("#1) ".21 (hi0) F o I 2 0 A29 OUTPUT Az i J6 MAJOR 1 MINOR )NTERVAL T INTERVAL SWITCH SWITCH )1- k (L0: 60 C770 '29 C712 Cn+b Flfd Mfd OUTPUT CHANGE OVER swncn 5 l I I l l I ./.S:m. csu'ren CLICK Posnm CLA UDE LANGDQN RICHARDS EWARD dAMES GLAZSHEE IN V EN TORS.

AGENT.

Patented Apr; 8, 1952 MULTIBAND BESONANT SYSTEM] WHEREIN EACH BAND IS STEP-WISE TUNABLE Claude Langdon Richards and Edward James Glaisher, London, England, assignors to The Hartford National Bank and Trust Company, Hartford, Conn., as trustee Application August 5, 1947, Serial No. 766,172 In Great Britain February 1, 1945 Section 1, Public Law 690, August 8, 1946 Patent expires February 1, 1965 Claims. 1

This invention relates to frequency determining circuit arrangements of the kind comprising a number of inductances and condensers together forming a resonant circuit having only one resonant frequency and which is tunable over a band of frequencies Ft-Fo, this band of frequencies being divided into m major subbands of substantially equal width and each major sub-band being divided into n substantially equal minor increments AF, switching means being provided whereby the minor elements corresponding to any desired multiple of AF up to a nAF can be selected while at the same time selecting any one of the major elements corresponding to the m major bands. Preferably the incremental minor elements are chosen to give exactly equal frequency increments AF when associated with one particular major element, whereas each of the remaining major elements is so adjusted that at two frequencies lying within the frequency band corresponding to that major, the frequency increment is an exact multiple of AF as described and claimed in our co-pending application No. 764,885, now issued as Patent No. 2,496,177, January 31, 1950.

According to the present invention, at least one of the interval switches and preferably both the major interval switch and the minor interval switch are duplicated or provided with an additional selector arm. In the case of the major interval switch the two arms are spaced by a predetermined major interval AFm whereas in the case of the minor interval switch the two arms are spaced by a predetermined minor interval AFn. An auxiliary switch may be provided whereby either combination of switch arms is utilised, giving a choice of, two resonant frequencies differing by the fixed amount AFm+AFn. Such a switch arrangement enables the circuit to be used as the sole frequency determining element of a combined transmitterreceiver, where it is desired to change the frequency by a constant interval on changing from transmit to "receive and vice versa. For this purpose the auxiliary switch can be coupled with the change-over switch.

For a better understanding of the invention,

reference is made to the following detailed description thereof to be read in connection with the accompanying drawing, wherein:

Fig. 1 is a schematic diagram of one preferred 2 switches, a minor interval switch K1 with two switch arms K11 and K12 set at a predetermined spacing corresponding to a minor interval AFn, and a major interval switch K2 with two switch arms K21 and K22 set at a predetermined spacing corresponding to a major interval AFm.

To give m major intervals for each of the arms K21 and K22, the number of major ele ments LmCo required is m=mu. where a. is an integer determined by AM. Arms K21 and K22 are arranged to engage successively the fixed contacts I, 2, 3, etc., of switch K2, each contact being connected to a major resonator element Lm1Co1, Lm2Co2, etc. Similarly to give n minor intervals for each of the arms K11 and K12, the number of minor elements Cn required in addition to Cm (the eifective capacity in the zero position of the arm K11) is n':n+b where b is an integer determined by AM. Thus arms K11 and K12 are arranged to engage successively contacts 0, I. 2, etc. of switch K1, each contact being connected to a minor element Cnc, Cm, Cn2, etc. The numbers of major and minor elements are related to the frequency range Ft-F0 and the basic minor increment AF by the relationship m 77. --AF The arms K11 and K21 are connected in common via lead 20 to one terminal of a change over switch K1, and the arms K12 and K22 are connected in common via lead 2| to the other terminal, so that operation of the switch K2 changes the frequency by a predetermined amount AFm-f-AFTL.

Another circuit arrangement according to the present invention is shown diagrammatically in Fig. 2 of the accompanying drawings. This arrangement which is adapted more particularly for main a transmitter-receiver, differs from the circuit shown in Fig. 1 primarily in that the major interval switch K2 has three switch arms K21, K22 and K2; set at intervals corresponding to two major intervals, the minor interval switch K, has only one switch arm, whereas the change over switch has three arms K31, K32 and K3: coupled so as to be adjusted simultaneously to one of the three positions S, R1 and R2, corresponding to the send position and first and second "receive positions.

The major elements each consist of the parallel connection ofinductance and capacity as shown for the major position ID. The inductance Lmm is connected in parallel with a main condenser C010 and a trimmer condenser Co'm to enable the major interval AFm to be pre-set to the required degree of accuracy. If desired, provision may also be made for trimming to inductance Lmm. 'The minor elements each consist of a capacity Cm, C712 etc., with provision for trimming as, for example, by means of a trimmer Ct connected in parallel with a minor element. With one selected major it is possible to trim all the minors to give zero frequency deviation from the nominal interval AIM, and to trim each major so that the frequency deviation is zero at two positions of the minor switch, in accordance with the invention claimed in U. S. Patent No. 2,496,177.

A major element selected by one of the arms &1, K22 and K23 in accordance with the setting of the change-over switch K1 is connected in parallel with the minor element selected by the switch K1 to determine the frequency. The major intervals may for example be 100 kc./s. and the minor intervals kc./s. The auxiliary condensers C21, C22, C23 enable the'change in frequency on switching over from K21 to 'Kzz or from K22 to K23 to be different from the frequency difference determined by the major intervals AFm. Thus, with major intervals of 100 -kc./sec. and the spacing K2lK22 and K22-K23 equal to two major intervals as shown, the frequency change on switching K3 from S to R, or from R1 to R2 can be made equal to '230 kc./sec. instead of 200 kc./sec.

To enable finer tuning than the intervals AFn determined by the minor elements, viz. 5 kc./sec. in the numerical example quoted, a variable condenser C1 is provided which is constructed to have a click position at its centre point at which it is normally set. For fine tuning within the 5 kc./sec. steps, this condenser C1 is adjusted in the appropriate sense out of its centralposition. The condenser Cl may be furnished with a calibrated scale giving a direct reading of the adjustment effected in kc./sec.

A trimmer condenser C2 enables the values of the major and minor elements to be adjusted'for correct frequencies with a nominal capacity and later trimmed to the same capacity when in the circuit to be used.

An adjustable condenser C3 which is in circuit only when the switchKz is in one of the receive" positions R1 or R2, enables the receiver to be aligned to another transmitter which is slightly off tune.

The appropriate values for the components can be ascertained in the manner described in the said U. S. Patent .No. 2,496,177. Similarly, the variants in circuit arrangement indicated'inthat application may be utilised in thepresent case.

We claim:

1. A frequency-determining adjustable resonant system comprising aseries of resonant circuits each tuned to a predetermined frequency. the frequencies of said circuits being uniformly spaced, a first multi-contact switch having "a movable arm for successively engaging each of said contacts, each of said contacts in 'said first switch being connected to one end of a respective circuit, the other ends of said circuits being interconnected, a series of reactanceelements having mutually different values, a second multicontact switch having a movable arm for successively engaging each of said contacts, each of said contacts in said second switch being connected to one end of a respective element, the other ends of said elements being interconnected, one of said first and second switches further in- 4 cluding an auxiliary movable arm coupled for simultaneous movement with the movable arm thereof and spaced a predetermined number of contactsirom said movable arm, a pair of output terminals the first of which is connected to both the interconnection of said circuits and the interconnection of said elements, and means to connect selectively the second of said terminals in one position to the movable arms of both said first and second switches and in another position to the auxiliary movable arm of said one of saidswitches.

2. A frequency-determining adjustable resonant system comprising a series of resonant circuits each tuned to a predetermined frequency, the frequencies of said circuits being uniformly spaced, a first multi-contact switch having a movable arm for successively engaging each of said contacts and an auxiliary movable arm coupled for simultaneous movement with the movable arm and spaced -a predetermined number of contacts therefrom, each of said contacts in said first switch being connected to one end of a respective circuit, the other ends of said circuits being interconnected, a series of reactance elements having mutually different values, a second multi-contact switch having a movable arm for successively engaging each of said contacts and an auxiliary movable arm coupled for simultaneous movement with the movable arm and spaced a predetermined number of contacts therefrom, each ofsaid contacts in said second switch being connected'to one end of a respective element, the other ends of said elements being interconnected, the movable arms of said first and second switches being interconnected,-the auxiliary arms of said first and second switches being interconnected, a pair of output terminals the first of which is connected to both the interconnection of said circuits and the interconnection of said elements, and means to connect selectively the second of said terminals in one position to the interconnection of the movable arms and in another position to theinterconnection of the auxiliary movable arms.

3. A frequency-determining adjustable resonant system comprising a series of resonant circuits each tuned to a predetermined frequency, the frequencies of said circuits being uniformly spaced, a first multi-contact switch having a movable arm for successively engaging each of said contacts and an auxiliary movable arm coupled for simultaneous movement with the movable arm and spaced a predetermined number of contacts therefrom, each of said contacts in said first switchbeing connected to one end of a respective circuit, the other ends of said circuits being interconnected, a series of reactance elements having respective values effecting uniform changes in the resonant frequency of one of said circuits when successively connected thereacross, a second multi-contact switch having a movable arm for successively engaging each of said contacts and an auxiliary movable arm coupled for simultaneous movement with the movable arm and spaced a'predetermined number of contacts therefrom, each of said contacts in said second switch being connected to one end of a respective element, the other ends of said elements being interconnected, the movable arms of said first and second switches being interconnected, the auxiliary arms of said first and second switches being interconnected, a pair of output terminals the first of which is connected to both the interconnection of *said circuit and the interconnection of said elements, and a selector switch arranged to connect in one position the second of said terminals to the interconnection of said movable arms and in another position to connect the said second of said terminals to the interconnection of said auxiliary movable arms.

4. A frequency-determining adjustable resonant system comprising a series of resonant circuits each tuned to a predetermined frequency, the frequencies of said circuits being uniformly spaced, a first multi-contact switch having first, second and third movable arms for successively engaging each of said contacts, said arms being coupled for simultaneous movement and being spaced a predetermined number of contacts from each other, each of said contacts in said first switch being connected to one end of a respective circuit, the other ends of said circuits being interconnected, a series of reactance elements having mutually different values, a, second multicontact switch having a movable arm for successively engaging each of said contacts, each of said contacts in said second switch being connected to one end of a respective element, the other ends of said elements being interconnected, a pair of output terminals the first of which is connected to both the interconnection of said circuits and the interconnection of said elements and the second of which is connected to the movable arm of said second switch, and means to connect the second of said terminals selectively to said first, second and third movable arms of said first switch.

5. A frequency-determining adjustable resonant system comprising a series of resonant circuits each tuned to a predetermined frequency,

having mutually different values, a second multicontact switch having a movable arm for successively engaging each of said contacts, each of said contacts in said second switch being connected to one end of a respective element, the other ends of said elements being interconnected, a pair of output terminals the first of which is connected to both the interconnection of said circuits and the interconnection of said elements and the second of which is connected to the movable arm of said second switch, means to connect the second of said terminals selectively to said first,

second and third movable arms of said first switch, and a variable reactance element having a click position at its center point connected across said pairs of terminals.

CLAUDE LANGDON RICHARDS.

EDWARD JAMES GLAISHER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Name Date Banfield Sept. 24, 1940 Number 

